Process for subchannel bandwidth allocation and extraction by an ISDN communications controller

ABSTRACT

A system includes a plurality of end-user devices coupled to a communications controller which is connected to an integrated services digital network (ISDN) line of a telecommunications network. The ISDN line has two bearer channels bandwidth and a data channel. A method of subchannel bandwidth allocation from the bearer channels is initiated by establishing, as demanded for a particular end-user device, a call connection though the telecommunications network between the communications controller and another network terminator. The controller inquires, over the data channel, whether the network terminator is a compatible communications controller. If a positive compatibility indication, the two controllers allocate to the particular end-user device a subchannel from the bandwidth of the two bearer channels, wherein the subchannel consists of bandwidth up to the full bandwidth if the particular end-user device is a data processing unit or bandwidth sufficient for a controller-encoded voice signal if the particular end-user device is a telephone. If the positive compatibility indication is not received, allocating by the communications controller to the particular end-user device one of the two bearer channels.

This application claims benefit to U.S. provisional application SerialNo. 60/013,174, filed Mar. 12, 1996.

BACKGROUND OF THE INVENTION

This invention relates generally to digital communications systems and,in particular, to a system having a communications controller providingaccess to an integrated service digital network (ISDN).

Devices for interfacing multiple analog telephones to an ISDN line of atelecommunications network are known. For example, International PCTapplication WO 95/22218 published on Aug. 17, 1995 and U.S. Pat. No.5,305,312 issued on Apr. 19, 1994 disclose such devices. However, theseknown devices only support a maximum of two telephones in concurrentuse.

It is desirable to support more concurrently active telephones over thesingle ISDN line.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improvedISDN communications controller.

The invention, therefore, according to a first aspect provides in asystem having a plurality of end-user devices coupled to acommunications controller which is connected to an integrated servicesdigital network (ISDN) line of a telecommunications network, the ISDNline having two bearer channels of predetermined bandwidth and a datachannel, a method of subchannel bandwidth allocation comprising thesteps of: establishing, as demanded for a particular end-user device, acall connection though the telecommunications network between thecommunications controller and another network terminator; inquiring,over the data channel, whether the network terminator is a compatiblecommunications controller; responsive to receiving a positivecompatibility indication, allocating by the two controllers to theparticular end-user device a subchannel from the predetermined bandwidthof the two bearer channels, wherein the subchannel consists of bandwidthup to the predetermined bandwidth if the particular end-user device is adata processing unit or bandwidth sufficient for a controller-encodedvoice signal if the particular end-user device is a telephone;responsive to not receiving the positive compatibility indication,allocating by the communications controller to the particular end-userdevice one of the two bearer channels; and transmitting, over thesubchannel or one bearer channel, outgoing signals from and incomingsignals to the particular end-user device.

A home access network controller, manifesting the present invention, isa device that may interface subscriber premises telephone equipment witha public switched telephone network, through an ISDN interface. It isintended for residential or small office application, where it providescertain efficiencies and conveniences not previously available in thatsetting. A primary advantage is the capacity to support more than twoand up to five telephones in concurrent use.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following descriptionof a home access network controller (HANC) system together withreference to the accompanying drawings, in which:

FIG. 1 is a schematic representing a first application of the HANCsystem;

FIG. 2 is a block diagram depicting functional elements of the HANC;

FIG. 3 illustrates an exemplary partitioning for the bandwidth of theISDN bearer channels;

FIG. 4 is a schematic representing a second application having a HANCand distributed internal line interface (DILI) to provide single linevoice distribution; and

FIG. 5 is a block diagram depicting functional elements of the HANC andDILI.

DETAILED DESCRIPTION

Referring to FIG. 1, for illustration of the present invention anapplication of the home access network controller (HANC) system isdiagrammed. Two HANC 10 communication controller devices are shown,labeled A and B respectively, which typically would be installed inseparate subscriber residences and interconnected through a backbonenetwork that provides many readily connectable full-duplex channels ofcommunications, namely a public switched telephone network (PSTN) 12.Each HANC 10 connects to the PSTN 12 via its own ISDN Basic RateInterface (BRI) line 14, consisting of two 64 Kbps bearer (B) channelsand one 16 Kbps data (D) channel multiplexed together on the sametwisted pair. Coupled to the HANC 10 at each subscriber residence aresubordinate devices, such as, one or more personal computers (PC) 16connected via an Ethernet local area network (LAN) 18, and up to fiveplain ordinary telephony service (POTS) telephones 20 connected in astar configuration via analog lines 22 which support dual tonemulti-frequency (DTMF) and switch-hook signaling with analog voice.Additional terminal device types (not shown) may be supported.

The HANC 10 represents the subscriber telephone equipment to the PSTN 12and functions as both a router and a dynamic bandwidth controller. Itaccepts calls announced on the BRI D-channel and routes them to the PC16 or the appropriate telephone 20, each of which may be identifiedexternally at the PSTN 12 by a unique directory number (DN). Converselyit delivers calls originating among its local subordinate devices, forexample, from a particular telephone 20 to a remote telephone 24 or fromthe PC 16 to an Internet Access Provider 26. The HANC 10 convertssignals to and from the lines 14, 22 between analog voice and either 64Kbps pulse code modulation (PCM) or 24 Kbps modified adaptivedifferential PCM (ADPCM) which supports an eight-to-three bitcompression, depending on whether the remote device to which it isconnected through the PSTN 12 is another HANC. It also acts as a networkgateway for PC protocols, encapsulating LAN packets for transmission onthe ISDN B-channels.

Referring to FIG. 2, the HANC 10 is characterized by various functionalelements which comprise an ISDN BRI interface 30, D-channels protocols32, bandwidth control 34, selectable coders/decoders (CODECs) 36, POTSinterfaces 38, Ethernet interface 40 and base logic 42.

The ISDN BRI interface 30 provides the physical bi-directional interfaceto the ISDN line 14 of the PSTN, and separates or combines the D-channeland two B-channels while deriving the line clock. It informs the baselogic 42 of line status.

The D-channel protocols 32 supports the physical and link layers for theQ.931 protocol with a central office of the PSTN and an X.25-basedprotocol with a remote HANC. Command and response packets are passed toand from the base logic 42.

The bandwidth control 34 connects digital voice to or from the CODECs 36with subchannels assigned among the 128 Kbps total bandwidth of theB-channels combined, as directed by the base logic 42. In other words,each B-channel supports a 64 Kbps transmission rate in the form of 8,0008-bit octets per second, and the bandwidth control 34 utilizes thecombined bandwidth of 128 Kbps to multiplex the digital voice by timedivision thereby creating communication subchannels in the B-channelbandwidth. Data derived from or destined to an attached PC can also bedirected to or from such a subchannel.

The selectable CODECs 36 encode analog voice signals to digital PCM orADPCM and decode PCM or ADPCM to analog, as selected by the base logic42. A CODEC 36 segregates the transmitted and received analog signals.It is the actual source (on its digital side) of the various signalingtones said to be issued on the POTS interface 38 below. There is oneCODEC 36, logically at least, for each subordinate telephone.

The POTS interface 38 supports the subordinate analog telephones, oneeach, providing the physical interface including DC current. It detectsswitch-hook transfer and DTMF tones, reporting both to the base logic42. As directed by the base logic 42, it issues dial tone, busy tone,remote ringing tone and local ringing AC and passes the bi-directionalvoice signal.

The Ethernet interface 40 connects the residential personal computer viaIEEE 802.3 physical and link protocols, providing packetized data to andfrom the base logic 42 at the rate of 10 Mbps.

The base logic 42 is the processing manager of the HANC. At power-on itoperates verification diagnostics, boots the operational software andseeks to establish connection with the PSTN central office on the BRID-Channel and with the PC. It communicates with the central office or aremote HANC via packets generated or examined on the D-channel. It makesthe bandwidth assignments executed by the bandwidth control 34 and mayexchange PC packets for transmission in or reception from a B-Channel.It understands call control sequences and directs the selectable CODECs36 and POTS interfaces 38 to execute them. It monitors the state of theHANC 10 device and attempts to recover from device failure by performingreset and restart. It keeps a status record accessible by the PC.

The HANC 10 and specifically the base logic 42 supports two categoriesof function in communication with an attached PC on the Ethernetinterface 40. It maintains a TCP socket by which PC software may exertcontrol and obtain status. It also passes PC packets through to thebandwidth control 34 for inclusion in the B-channels, and vice-versa,when the PC is connected on the public network.

According to a particular implementation, the base logic 42 may beeffected by a microprocessor operating under appropriate software, andthe bandwidth control 34 may be a set of shift registers. Alternatively,a digital signal processor (DSP) might be used in which case it couldintegrate several other functional elements. Low cost integratedcircuits are commercially available to support the CODEC 36 function andthe POTS interface 38, but for supporting only five telephone ports muchof that logic could be provided by the DSP. The Ethernet interface 40 isconventional functionality that may be implemented in separate hardware.However, with an aggregate signal bandwidth remaining of only 144 Kbps,or 6.9 microseconds per bit, or 116 DSP instructions per bit (60nanoseconds each), and no algorithmic challenge worse than a PCM/ADPCMlookup table, a single DSP may perform all HANC logic above the physicallayer.

Turning back to FIG. 1, in operation each HANC 10 may support at leasttwo concurrently active calls, for instance, with two of its subordinatetelephones 20 or one telephone 20 and the PC 16 connected externally,using the two B-channels on the BRI line 14 independently with eachseparately routed and connected. Alternately, if the only current useris the PC 16, both B-channels may be connected to the Internet AccessProvider 26 thereby delivering maximum bandwidth of 128 Kbps. For atelephone connection, the HANC 10 may convert between analog voice andthe PCM-encoded voice required on a B-channel, using 64 Kbps.

If the remote connection is another HANC 10, however, additionalconnectivity is available. In this case analog voice from the telephones20 is converted to 24 Kbps ADPCM before application to a B-channel. Whenboth B-channels are available between the two compatible HANCs 10, up tofive telephones 20, each using a three-bit allocation as a voicesubchannel, and the PC 16 using a one-bit allocation as a datasubchannel, may converse concurrently with their counterparts on the 16bits derived from the 8-bit octets of both B-channels combined.

In FIG. 3, illustrated is an exemplary partitioning of the B-channel8-bit octets to provide multiple communication subchannels whereby theup to five telephones and PC may communicate simultaneously over theISDN line. In the 8-bit octets of the first B-channel, bandwidth definedby bits 1-3 may be allocated as a voice subchannel which is labeled VS1and bits 4-6 as another voice subchannel VS2, in support of two separatetelephone calls. For a third active telephone call, the voice subchannelVS3 bandwidth may occupy bits 7-8 of the first B-channel and bit 1 ofthe second B-channel. A fourth and fifth telephone call may be allocatedvoice subchannels VS4 and VS5 which occupy bits 2-4 and 5-7,respectively, of the second B-channel bandwidth of which the remainingbit 8 may be employed as a data subchannel DS for PC communications.

If only one B-channel is available for HANC-to-HANC communications, forexample, because the other is busy with the remote telephone 24 shown inFIG. 1, two telephones 20 and the PCs 16 may converse concurrentlybetween HANCs. In this case, the 8 bit frame of the one B-channel forHANC-to-HANC communications may be partitioned into two three bit voicesubchannels and a two bit data channel. If the call is only between PCs16, all available bandwidth is allocated to that connection, else threebits for each ADPCM voice subchannel. The HANC 10, or HANCs 10-A and10-B in consultation, manage this bandwidth automatically in all cases.

The HANC 10 deallocates bandwidth when a call disconnects. It may alsodeallocate (i.e., deallocate and reallocate) when a new call originatesor arrives. In the case of two HANCs 10-A and 10-B originally connectingonly their PCs 16, a subsequent call between subordinate telephones 20requires deallocating three bits from the PC data subchannel toconstruct a new voice subchannel, but requiring consultation onlybetween HANCs. The more drastic case is a new call between a subordinateand an independent remote telephone, namely telephone 24. An entireB-channel must be deallocated from the HANCs 10 in this case anddiverted to serve the new call. This is accomplished by communication onthe D-channel between HANCs as well as the PSTN 12 central office. Inany case, if the necessary bandwidth is not available because too muchis already allocated to relatively inflexible voice traffic, the newcall is rejected on the D-channel or indicated busy to the subordinatetelephone 20.

When a first connection is established between a HANC (e.g., the HANC10-A) and a remote device through the PSTN 12, the HANC 10-A asks theremote if it is also a HANC using the X.25 protocol permitted end-to-endon the D-channel. If there is no valid response the HANC 10-A treats thenew call as POTS-to-POTS, but if a HANC identification is received(e.g., from the HANC 10-B), subsequent signaling between the two HANCs,10-A and 10-B, discloses the subsystem controlled by each as well as itscurrent state. At the end of this exchange, requiring at most a fewhundred milliseconds, each HANC 10-A and 10-B knows the devicesconnected to the other, their DNs, whether each is busy and how muchbandwidth is available for allocation.

The following describes in more detail particular processes forsubchannel bandwidth allocation and for external bandwidth extractionthat may be adapted to the HANC system of FIG. 1.

Once the connection exists via a channel through the PSTN 12 between thetwo HANCs 10-A and 10-B, the effect of subchannel bandwidth allocationis to permit complex data flow between the individual PCs, referenced as16-A and 16-B, simultaneously with multiple separate conversationsbetween telephone sets 20 on the two HANCs 10, without calling upon thePSTN 12 for assistance. The HANCs 10-A and 10-B accomplish this bycreating subchannels on the common network channel using time divisionmultiplexing. Subchannels exist only as demanded by the traffic andfunction by appropriating a part of the full bandwidth as negotiatedbetween the HANCs 10-A and 10-B. In the absence of demand for multiplesubchannels most of the bandwidth is allocated to the single user. Ifthat is a PC, its data are free to flow at the maximum rate.

Negotiation between HANCs 10 requires a subchannel reserved to suchspecial communication. This is assigned that minimum of the channelbandwidth appropriate to timely negotiation and is called the controlsubchannel.

The process of allocating and removing subchannels is initiated by enduser demand. An end user of one of the HANCs, such as the PC 16-A atHANC 10-A, first causes the initial connection through the PSTN 12 toanother terminator, such as HANC 10-B. HANC 10-A inquires via thecontrol subchannel whether that terminator is a compatible HANC. In theabsence of a positive response it permits the PC 16-A to communicate byits default protocol, if one exists, or breaks the connection withsuitable notification. If HANC 10-B responds, demonstratingcompatibility, the two controllers proceed to open the full channelbandwidth, less that of the minimal control subchannel, to communicationbetween the two PCs 16-A and 16-B. If the initial connection isrequested by an analog telephone set 20, such as 20-A1, the HANC 10-Astill elicits the compatibility indication. In its absence the “naturalbandwidth” required of ordinary voice communication, 64 Kbps PCM, isallocated and no suballocation on that B-channel is possible for theremainder of the call. If telephone set 20-A1 called a compatibletelephone, such as 20-B2, however, the HANCs 10-A and 10-B allocate the24 Kbps of bandwidth as required by the ADPCM voice encoding, with therest held in reserve for further demand.

Subchannel allocation employs the following steps, given the connectionalready established between PC 16-A and PC 16-B. As part of the initialcompatibility exchange, each HANC 10-A and 10-B informed the other ofthe identifiers, i.e., telephone numbers, and types of all attachedend-user devices.

1) User at telephone 20-B3 dials the DN of telephone 20-A2.

2) HANC 10-B notifies 10-A of this demand and proposes the extraction ofa specified part of the current PC bandwidth to support the telephoneconversation, using the control subchannel.

3) HANC 10-A investigates the state of telephone 20-A2, which may beidle, busy or non-working, and reports accordingly. If idle itinstigates ringing at that telephone while HANC 10-B reflects a ringingtone to telephone 20-B3.

4) If no user answers telephone 20-A2, the user at telephone 20-B3eventually abandons the call and HANC 10-B so notifies HANC 10-A.

5) If telephone 20-A2 answers, HANC 10-A ceases to ring and accedes tothe suballocation request. Coincident with an accession messagetransmitted on the control subchannel, HANC 10-A extracts sufficientbandwidth from the PC subchannel to form the specified voice subchannel.After a specified period upon or after the close of the accessionmessage, HANC 10-A effects the bandwidth changeover in its full channeltransmission toward HANC 10-B.

6) HANC 10-B transmits an acknowledgment on the control subchannel.After a specified period upon or after the close of the acknowledgmentmessage, HANC 10-B effects the bandwidth changeover in its transmissionstoward HANC 10-A. Note that by measuring from the close of the accessionand acknowledgment messages, synchronization of bandwidth changeover isobtained with bit-level timing accuracy. Also, the point in time whenthe bandwidth changeover is effected upon or after the close of theaccession and acknowledgment messages may be predetermined, whetherimmediate or after a fixed time period.

7) Voice communication proceeds on the new subchannel, using the ADPCMencoding method, simultaneously with data transfer on the PC subchannel.Additional voice subchannels may also be opened by the same process. Theonly effect apparent upon interPC communications is a reduction inthroughput, which may or may not be of concern.

8) The user at telephone 20-A2 hangs up.

9) HANC 10-A sends a deallocate message to HANC 10-B on the controlsubchannel, identifying the voice subchannel to be deallocated. After aspecified period upon or after the close of the deallocation message,HANC 10-A restores that amount of bandwidth to the PC subchannel andeffects the bandwidth changeover in its transmissions toward HANC 10-B.

10) HANC 10-B sends an acknowledgment message to HANC 10-A and likewisechanges over to the larger PC subchannel bandwidth after theacknowledgment is complete.

Part of the bandwidth used between two HANCs 10 may be extracted topermit communications with outside devices, such as, the independentanalog telephone 24. The process of extracting bandwidth is initiated byend user demand, either from outside the context of two connected HANCs10-A and 10-B, or from a dependent user of a particular HANC 10 whowishes to communicate with an outsider.

Bandwidth extraction can be performed even when the HANCs 10 are usedonly by attached telephones 20. The process is best illustrated,however, by its operation when the principle communication is betweenPCs 16.

As part of the initial compatibility exchange, each HANC 10 informed theother of the identifiers, i.e., telephone numbers, and types of allattached end-user devices.

Outsider initiated extraction involves the following steps:

1) User at telephone 24 dials the DN of the telephone 20-A2 connected toHANC 10-A.

2) The PSTN 12 notifies the HANC 10-A of the incoming call, usingprocesses equivalent to “Call Waiting” and “Caller-ID” as conventionallypracticed.

3) HANC 10-A examines its outstanding bandwidth allocation. If bandwidthinsufficient to support standard network voice remains unassigned orsuch bandwidth cannot be removed from PC support without disconnectingany conversation or exchange already in progress, it ignores or rejectsthe incoming call, according to the appropriate backbone networkprotocol.

4) If the necessary bandwidth can be found, however, HANC 10-A notifiesHANC 10-B of the demand, using the control subchannel, and proposes theextraction of a sufficient part of the current PC bandwidth to supportordinary voice.

5) HANC 10-B accedes to the extraction request. Coincident with anaccession message transmitted on the control subchannel, B extractssufficient bandwidth from the PC subchannel to form the specified voicesubchannel. After a specified period upon or after the close of theaccession message, HANC 10-B effects the bandwidth changeover in itsfull channel transmission toward HANC 10-A.

6) HANC 10-A transmits an acknowledgment on the control subchannel.After a specified period upon or after the close of the acknowledgmentmessage, HANC 10-A effects the bandwidth changeover in its transmissionstoward HANC 10-B. Note that by measuring from the close of the accessionand acknowledgment messages, synchronization of bandwidth changeover isobtained with bit-level timing accuracy.

7) HANC 10-A accepts the incoming call by notifying the PSTN 12 andcreates an internal path for communication between telephones 20-A2 and24.

8) Voice communication proceeds on the extracted channel, using thenetwork standard encoding method, simultaneously with data transferbetween HANCs 10 on the PC subchannel. Additional voice subchannels mayalso be opened between the HANCs 10, using a different process. The onlyeffect apparent upon interPC communications is a reduction inthroughput, which may or may not be of concern.

Insider initiated extraction involves the following steps:

1) The user at telephone 20-A2 dials a DN not administered by HANC 10-B,such as the number corresponding to telephone 24.

2) HANC 10-A examines its outstanding bandwidth allocation. If bandwidthinsufficient to support standard network voice remains unassigned orsuch bandwidth cannot be removed from PC support without disconnectingany conversation or exchange already in progress, it informs thetelephone 20-A2 user that local circuits are busy.

3) If sufficient bandwidth is found, however, HANC 10-A notifies HANC10-B of the demand, using the control subchannel, and proposes theextraction of a sufficient part of the current PC bandwidth to supportordinary voice.

4) HANC 10-B accedes to the extraction request. Coincident with theaccession message transmitted on the control subchannel, B extractssufficient bandwidth from the PC subchannel to form the specified voicesubchannel. After a specified period upon or after the close of theaccession message, HANC 10-B effects the bandwidth changeover in itsfull channel transmission toward HANC 10-A.

5) HANC 10-A transmits an acknowledgment on the control subchannel.After a specified period upon or after the close of the acknowledgmentmessage, HANC 10-A effects the bandwidth changeover in its transmissionstoward HANC 10-B.

6) HANC 10-A notifies the PSTN 12 of its call to the DN of telephone 24using an appropriate part of its full channel bandwidth and assigns thatportion to network control, permitting the user at telephone 20-A2 tohear the network call progress reports.

7) If the telephone 24 answers, voice communication between telephones20-A2 and 24 proceeds on the extracted channel, using the networkstandard encoding method, simultaneously with data transfer betweenHANCs 10 on the PC subchannel.

8) The user at telephone 20-A2 hangs up.

9) HANC 10-A notifies the PSTN 12 that the connection between telephones20-A2 and 24 no longer exists.

10) HANC 10-A sends a restore bandwidth message to HANC 10-B on thecontrol subchannel, identifying the voice subchannel to be restored foruse by the PCs 16. After a specified period upon or after the close ofthe restore message, HANC 10-A restores that amount of bandwidth to thePC subchannel and effects the bandwidth changeover in its transmissionstoward HANC 10-B.

11) HANC 10-B sends an acknowledgment message to HANC 10-A and likewisechanges over to the larger PC subchannel bandwidth after theacknowledgment is complete.

In application of the above processes for subchannel bandwidthallocation and bandwidth extraction to the HANC system, the ISDND-channel may be utilized for the control subchannel. If the initialconnection through the PSTN 12 is established between PCs 16, the calledHANC furnishes the DN of its second B-channel as part of thecompatibility exchange and the calling HANC immediately calls throughthe PSTN 12 on the second B-channel, thus obtaining the maximum 128 Kbpsfor use in passing PC data. Subsequent demands by telephones 20 to sharethe bandwidth are negotiated on the D-channel as previously described.

Connections through the PSTN 12 are obtained using the ISDN standardQ.931 protocols on the D-channel. The calling HANC sends a compatibilityinquiry via the end-user protocols on the D-channel, which are specifiedto agree with X.25 standards. If it receives the compatibility indicatoras an X.25 response, the call proceeds as described above.

Notifications by the PSTN switch of incoming calls, such as the onedescribed from telephone 24, arrive on the D-channel in the switchsupported protocol. Subsequent negotiations between HANCs 10 use X.25protocols. The extraction of bandwidth to support the voice demandproceeds as previously described. Here an entire 64 Kbps B-channel mustbe allocated to the external PCM voice flow. Only one such externalconnection can be supported simultaneously with the interHANCconnection, which uses the other B-channel. That B-channel can still besubdivided, however, among PCs 16 and telephones 20 attached to the twoHANCs 10-A and 10-B.

A further feature supported by the HANC 10 is a method for convenientcall acceptance. To obtain the convenience of answering a telephone callin any part of a residence, a traditional method would place extensiontelephones in every part where such convenience is desired. This methodbears the disadvantage that so long as an extension is busy, all theothers are unavailable for separate use.

When the convenient call feature is active on the HANC 10, it rings allits idle telephones 20 simultaneously with a distinctive ringingpattern, preassigned according to DN, upon receipt of a call intendedfor any one of the DNs. That is, at the switch in the PSTN 12, the ISDNline 14 of the HANC 10 is represented by six DNs, one for the PC 16 andone for each analog telephone 20. Each DN is identified by its ownpattern of long rings, short rings or variably spaced longs and shorts.The HANC 10 maintains the association between the DNs and correspondingdistinctive ring patterns, and it selects the appropriate pattern for anincoming call according to the dialed DN received over the data channelfrom the switch.

The first idle telephone seen by the HANC 10 to go off-hook is thenconnected to the incoming call. The other idle telephones remainavailable for another call, either outgoing or incoming, in which casethe same procedure is repeated. Furthermore, the same procedure ofcourse may be applied to incoming calls from another HANC. Describedabove is a process for connecting the incoming call to the telephonegone off-hook.

This method for convenient call acceptance is applicable to telephonesets 20 wired to the HANC 10 either in the star configuration shown inFIG. 1 or by a local voice distribution method, described in thefollowing.

The typical residential subscriber of telephone services uses a singletelephone line for distribution of the service within his residence.Though several telephone sets may be attached to that line, they alloperate interdependently as extensions and are represented by one DN atthe public switch.

FIG. 4 illustrates a variation in the HANC system that supports theattachment of up to five POTS telephones by a single telephone line, yetpermits each to converse independently of the others and to berepresented by its own DN at a central office of the PSTN. A HANC 50connects to the PSTN 52, via a national standard ISDN BRI line 54consisting of two 64 Kbps B-channels and a 16 Kbps (control) D-channel,multiplexed together on the external line 54. It supports the attachmentof a (i.e., one or more) PC 56 via 802.3 LAN 57. Up to five local analogtelephones 58 may be attached via respective distributed internal lineinterfaces (DILIs) 60 devices to the HANC 50 over a dual twisted pairdistribution line 62 located internal to a subscriber's residence.Additional device types may also be supported (not shown).

The HANC 50 interfaces with the public switch on the BRI D-channel andthus arranges connectibility through the PSTN 52. It is responsible fortransferring encoded voice between the ISDN B-channels and thedistribution line 62 to the DILIs 60 and for signaling the DILIs 60 toinform them of call progress. Each DILI 60 interfaces an analog POTSline 64 to the distribution line 62 from the HANC 30. It receives itsoperating power down that same line 62.

Referring to FIG. 5, illustrated are the functional elements of the HANC50 and the DILIs 60. The HANC 50 is similar to the HANC 10 embodiment inFIG. 2, except that the CODECs 36 and the POTS interfaces 38 are removedfrom the HANC 30 and now consigned to the DILIs 60, identified byreferences 36′ and 38′ respectively. In their place, the HANC 50receives a PCM converter 66. The digitally encoded voice signalsprovided by the bandwidth control 34, either in PCM or ADPCM form, aremade only PCM by the PCM converter 66 for transmission on thedistribution line 62 to the DILIs 60.

In each DILI 60, the CODEC 36′ converts analog voice to PCM voice andvice-versa passed between the POTS interface 38′ and a HANC interface68. The POTS interface 38′ provides an analog line connector, linetermination and impedance matching, pulse dial and DTMF detection, dialtone generator, busy tone generator, remote-ringing tone generator, anda ringing voltage generator. Functionality of the HANC interface 68includes a distribution line connector, DC power separation andpropagation on the distribution line 62, protocol support for callprogress communication with the HANC 50, distribution physical protocolsupport for frame detection and channel (i.e. time slot) identification,a configurator to assign distribution channels, and a bi-directionalframe redriver with drop-and-insert channel support. Each DILI 60 may beoptionally equipped with caller identification (ID) displaycapabilities.

The distribution line 62 from the HANC 50 is a double twisted pair,typical residence wiring, one pair for each direction. All DILIs 60 arepowered by DC on the combined pair. Signals are driven in a standarddigital manner, such as Manchester or NRZI encoding, capable of ACcoupling, at a bit rate relatively low but high enough to include fivedigital voice channels and five control channels in individual timeframes. Each frame consists of five time slots corresponding torespective DILIs 60, wherein each time slot includes one of the voicechannels and one of the control channels. The frame start is identifiedby recurrence of a fixed bit pattern. A control channel is used toinform the HANC 50 of the switch-hook status of a particular telephone58 and a dialed telephone numbers or DTMF tones detected. In the reversedirection it conveys instructions to issue ringing voltage, to issuedial tone, busy tone or ringing tone and to display a delivered callerID. In the inbound direction to the HANC 50, each DILI 60 uses adrop-and-insert technique, well known from T1 multiplexers, to insertits signals at the appropriate time slot.

Turning back to FIG. 4, the following illustrates the process to place acall from a DILI-connected telephone 58.

1) A user lifts receiver at a particular telephone 58.

2) The DILI 60 connected to that telephone 58 detects off-hook state andsignals the HANC 50 on that DILI's control channel.

3) The HANC 50 responds with an instruction for the DILI 60 to issuedial tone.

4) The DILI 60, responsive to the received instruction, generates dialtone to the receiver of the attached telephone 58.

5) The user keys a called DN in DTMF tones.

6) The DILI 60 detects these tones, and transmits numeric codes to theHANC 50 on the control channel.

7) On receipt of the first numeric code, the HANC 50 instructs the DILI60 to cease generation of the dial tone.

8) The HANC 50 requests connection to the called DN via itscommunications 54 with the central office of the PSTN 52. If the remotetelephone (i.e., called DN) is busy, the HANC 50 instructs the DILI 60to issue a busy tone. If the remote is being rung, the HANC 50 mayeither feed the remote ringing tones through to the DILI 60, if theswitch provides any, or instruct the DILI 60 to generate its own.

9) The DILI voice channels, inbound and outbound, are activated throughto the PSTN 52, with the DILI 60 performing basic analog to digitalcoding-decoding and the HANC 50 assuring compatibility with PSTN switchor remote HANC (if the called DN corresponds to such) requirements.

When a remote telephone calls the DN of a DILI-connected telephone, thefollowing process is effected.

1) The central office switch of the PSTN 52 notifies the HANC 50 of thecalled DN.

2) The HANC 50 determines the particular DILI 60 that owns this DN.

3) If the DILI 60 and the dependent telephone 58 are busy, the HANC 50so notifies the PSTN switch. Otherwise, via that DILI's control channel,the HANC 50 instructs the DILI 60 to generate ringing voltage and todisplay the caller ID.

4) A user lifts receiver at that telephone 58.

5) The DILI 60 informs the HANC 50 on the control channel that thetelephone 58 is off-hook.

6) The HANC 50 instructs the DILI 60 to end ringing voltage and toactivate its voice channels in both directions.

It is noted that the above processes are representative but notexhaustive.

If the local telephones 58 are connected to remote telephones notassociated with a remote HANC (not shown), only two of the telephones 58may be active simultaneously, one on each B-channel. If they aremediated by a remote HANC, however, in support of interfamilycommunications or small offices, up to five telephones 58 may be activeconcurrently, along with the PC 56. The method of interconnecting the upto five telephones through multiple HANCs was described above.

Those skilled in the art will recognize that various modifications andchanges could be made to the invention without departing from the spiritand scope thereof. It should therefore be understood that the claims arenot to be considered as being limited to the precise embodiment of thesystem set forth above, in the absence of specific limitations directedto each embodiment.

I claim:
 1. In a system having a plurality of end-user devices coupledto a communications controller which is connected to an integratedservices digital network (ISDN) line of a telecommunications network,the ISDN line having two bearer channels of predetermined bandwidth anda data channel, a method of subchannel bandwidth allocation comprising:establishing, as demanded for a particular end-user device, a callconnection through the telecommunications network between thecommunications controller and another network terminator; inquiring,over the data channel, whether the network terminator is a compatiblecommunications controller, wherein the compatible communicationscontroller has a plurality of end-user devices coupled thereto, andwherein the plurality of end-user devices includes a plurality oftelephones; responsive to receiving a positive compatibility indication,allocating by the two controllers to the particular end-user device asubchannel from the predetermined bandwidth of the two bearer channels,wherein the subchannel consists of bandwidth up to the predeterminedbandwidth if the particular end-user device is a data processing unit orbandwidth sufficient for a controller-encoded voice signal if theparticular end-user device is a telephone, and wherein the particularend user device is a data processing unit having been allocated thesubchannel of bandwidth up to the predetermined bandwidth as a datasubchannel; responsive to receiving the positive compatibilityindication, each of the two controllers informing the other, over thedata subchannel, of identifiers and types of coupled devices; responsiveto not receiving the positive compatibility indication, allocating bythe communications controller to the particular end-user device one ofthe two bearer channels; transmitting, over the subchannel or one bearerchannel, outgoing signals from and incoming signals to the particularend-user device; dialing, at a first telephone of the telephones coupledto one of the two communications controllers, the identifiercorresponding to a second telephone of the telephones coupled to theother controller; and the one controller sending, on the data channel, asuballocation request for a voice subchannel to the other controller,wherein the suballocation request includes the identifier of the secondtelephone and specifies extraction of bandwidth from the data processingunit subchannel for the voice subchannel; the other controllerinvestigating state of the second telephone, which state is either idle,busy or non-working, and reporting the state to the one controller; ifthe state is idle, the other controller instigating ringing at thesecond telephone and the one controller reflecting a ringing tone to thefirst telephone; if the second telephone is answered, the othercontroller ceasing to ring and transmitting on the data channel anaccession message, coincident with which the other controller extractingsufficient bandwidth from the data processing unit subchannel to formthe specified voice subchannel; after a specific period at close of theaccession message, the other controller effecting the bandwidthchangeover in its full channel transmission towards the one controller;the one controller transmitting an acknowledgement message on the datachannel; and after the specific period at close of the acknowledgementmessage, the one controller effecting the bandwidth changeover in itstransmissions towards the other controller; whereby voice communicationproceeds on the voice subchannel, using the controller-encoded voicesignal, simultaneously with data transfer on the data processing unitsubchannel.
 2. A method as claimed in claim 1, comprising the steps of:sending, responsive to either of the first or second telephones goingon-hook, a deallocation message from the one controller to which thattelephone is coupled to the other controller, wherein the deallocationmessage identifies the voice subchannel to be deallocated; after thespecific period at close of the deallocation message, the one controllerrestoring that amount of bandwidth to the data processing unitsubchannel and effecting the bandwidth changeover in its fulltransmissions toward the other controller; the other controllertransmitting an acknowledgement message on the data channel to the onecontroller; and after the specific period at close of theacknowledgement message, the other controller changing over to thelarger data processing unit subchannel bandwidth.
 3. A method as claimedin claim 2, wherein the specific period is a predetermined time intervalfollowing the close of any of the accession message, the deallocationmessage and the acknowledgement message.
 4. A method as claimed in claim2, wherein the specific period is immediately following the close of anyof the accession message, the deallocation message and theacknowledgement message.
 5. A controller for use with a basic rateintegrated services digital network (ISDN) service, the basic rate ISDNservice having a first bearer channel with a predetermined bandwidth, asecond bearer channel, and a data channel, the controller comprising: apartitioner, wherein the partitioner divides the first bearer channelinto a first partition and a second partition, such that each of thefirst and second partitions have less than the predetermined bandwidth;an allocation manager coupled to the partitioner, wherein the allocationmanager assigns the first partition to a telephone connection for atelephone and assigns the second partition to a second connection,wherein the second connection does not connect the same two end devices,such that the first bearer chapel is shared by two differentconnections, and wherein the second connection also includes bandwidthsimultaneously from the first and second bearer channels; a framercoupled to the allocation manager, wherein the framer insertsinformation into a frame for sending the information over the firstbearer channel in the partitioned bandwidth assigned to the telephoneconnection, and wherein the information originates at the telephone; anda deframer coupled to the allocation manager, wherein the deframerextracts information from a frame which is received over the firstbearer channel in the partitioned bandwidth assigned to the telephoneconnection, and wherein the information is intended for the telephone.6. The controller of claim 5, further comprising an analog-to-digitalconverter coupled to the framer, wherein the analog-to-digital converterconverts analog data into digital data using adaptive differential pulsecode modulation (ADPCM).
 7. The controller of claim 5, furthercomprising a digital-to-digital converter coupled to the framer, whereinthe digital-to-digital converter converts digital data in pulse codemodulation (PCM) format into adaptive differential pulse code modulation(ADPCM) format.
 8. A method of sharing bandwidth in a single firstbearer channel between two different connections, the first bearerchannel having a predetermined bandwidth and being part of an integratedservices digital network (ISDN) line, the ISDN line also having a secondbearer channel, the method comprising: partitioning the first bearerchannel into a first partition and a second partition, such that each ofthe first and second partitions have less than the predeterminedbandwidth; assigning the first partition to a telephone connection for atelephone; assigning the second partition to a second connection,wherein the second connection does not connect the same two end devicesas the telephone connection, and wherein the second connection alsoincludes bandwidth simultaneously from the first and second bearerchannels; packetizing information to be sent over the first bearerchannel in the partitioned bandwidth assigned to the telephoneconnection, wherein the information originates at the telephone; anddepacketizing information received over the first bearer channel in thepartitioned bandwidth assigned to the telephone connection, wherein theinformation is intended for the telephone.
 9. A controller for use withan integrated services digital network (ISDN) line, the ISDN line havinga first bearer channel with a predetermined bandwidth, a second bearerchannel, and a data channel, the controller comprising: an ISDNinterface; a bandwidth controller coupled to the ISDN interface, whereinthe bandwidth controller allocates available bandwidth from thepredetermined bandwidth of the first bearer channel, and wherein thebandwidth controller can allocate less than the entire predeterminedbandwidth to a connection thus allowing the first bearer channel to beshared by a telephone connection and another connection, wherein theanother connection does not connect the same two end devices as thetelephone connection does, and wherein the another connection alsoincludes bandwidth simultaneously from the first and second bearerchannels; and a coder/decoder coupled to the bandwidth controller,wherein the coder/decoder encodes information for transmitting over thefirst bearer channel in the bandwidth allocated to the telephoneconnection, and wherein the coder/decoder decodes information receivedover the first bearer channel in the bandwidth allocated to thetelephone connection.
 10. The controller of claim 9, wherein thebandwidth controller can deallocate and allocate individual connectionswithout affecting another existing connection which is sharing the firstbearer channel.
 11. The controller of claim 9, wherein two telephoneconnections share the first bearer channel.
 12. The controller of claim9, wherein two analog telephone connections share the first bearerchannel.
 13. The controller of claim 9, wherein the coder/decoder usesadaptive differential pulse code modulation (ADPCM) to encode analogtelephone signals.
 14. The controller of claim 9, wherein thecoder/decoder uses adaptive differential pulse code modulation (ADPCM)to encode digital pulse code modulation (PCM) signals.
 15. Thecontroller of claim 9, further comprising a plain ordinary telephonyservice (POTS) interface coupled to the coder/decoder.
 16. A method ofsharing bandwidth in a single first bearer channel between two differentconnections, the first bearer channel having a predetermined bandwidthand being part of an integrated services digital network (ISDN) line,the ISDN line also having a second bearer channel, the methodcomprising: allocating bandwidth from the first bearer channel to afirst connection which is a telephone connection and to a secondconnection, wherein the two connections do not connect the same two enddevices, and wherein the second connection also includes bandwidthsimultaneously from the first and second bearer channels; encodinginformation for transmission over the first bearer channel in thebandwidth allocated to the telephone connection; interfacing to the ISDNline; and decoding information received over the first bearer channel inthe bandwidth allocated to the telephone connection.